1. Field of the Invention
The present invention relates to a device for feeding single film sheets out from a stack of film sheets, particularly for use in a feed magazine for an X-ray film apparatus.
2. Background of the Invention
A feeding device for film sheets must ensure both that only a single sheet is fed at a time and that no artifacts are caused on the film sheet, such as scratches, pressure marks, static marks etc.
Many devices are known which make use of vacuum suction to pick up a film from the stack, but this solution is considered too complex and expensive.
Other known devices are based on a calibrated withdrawal slot, which has a width that allows the exit of only one film at a time. An example is given by U.S. Pat. No. 4,365,793, in which the film sheet is driven by a friction roller through the slot.
Other devices make use of a calibrated pushing claw or the like, which engages the edge of only one film at a time. An example is given by U.S. Pat. No. 3,955,092, in which film bending assists in the separation of the film from the stack.
Another known device is shown by U.S. Pat. No. 3,961,785. That device makes use of both a calibrated withdrawal slot and a calibrated pushing claw.
It has been found that known devices not only are too complex and expensive, but also very often cause damage to the film sheets. In particular, film sheets can easily be scratched while passing through a calibrated slot, since at least one side of the slot must be sharply angled to ensure film to film separation. Also pushing claws may easily scratch the film adjacent the film being pushed.